Objective.Antibodies against cardiolipin (aCL) are associated with increased risk of cardiowscular disease (CVD) in autoimmune diseases like SLE.As cardiolipin is easily oxidized, we here determine the role of IgM antibodies against oxidized cardiolipin (aOxCL) in CVD in a well characterized cohort.Methods.One third of sixty-year olds from the Stockholm County were included in a screening (2039 men and 2193 women), where 211 incident CVD-cases (myocardial infarction, ischemic stroke, or hospitalized angina pectoris) and 633 age-and sex-matched controls were identified through a 5-7 year follow-up of those initially recruited.Antibodies were determined by ELISA.Results.IgM aOxCL-levels were divided in quartiles with the lowest quartile set as the reference group.After adjustment for smoking, BMI, type Ⅱ diabetes, hypercholesterolaemia and high blood pressure an increased risk for CVD was determined in the lowest quartile of aOxCL values with a OR of 1.80 (confidence interval (CI) 1.12-2.91), p=0.0159.Strong associations were noted for men who in the lowest quartile had an increased OR for CVD of 2.46 (CI 1.34-4.53), p=0.0037 and for stroke: 12.28 (CI 1.48-101.77), p=0.02.Women in the highest quartile were protected against MI and in both men and women, high levels (reaching significance above 86th percentile) where associated with significantly decreased risk (data not shown).In contrast, antibodies against CL did not show any significant associations with CVD.Conclusions.aOxCL could be a novel risk/protection marker for CVD, with potential therapeutic implications.Further cohort data are needed to firmly establish the associations.